JPS609300A - Electrostatic type electroacoustic transducer and its manufacture - Google Patents

Abstract

PURPOSE:To prevent deterioration of a characteristic under the environmental condition in the course of use, storage and transport by sticking a diaphragm extended frame body consisting of a conductive material to a conductivity providing surface of a dielectric thin film, in a state that an electric connection is held, and thereafter, providing a water-repelling material layer on both main faces. CONSTITUTION:A polyethylene terephthalate film 1 of 4mum thick, on which an Ni-Cr alloy is vacuum vapor-deposited 2 is extended as an electric conductive layer on one surface, and a brass-made vibrating electrode fixed ring 4 whose outside diameter and inside diameter are 5mm. and 3.5mm., respectively is stuck to the Ni-Cr vapor-deposited surface by using an electroconductive adhesive agent 3, and they are formed as one body. Subsequently, the vibrating electrode formed in this way is immersed in a toluen solution in which a water-repelling silicone oil is dissolved, and thereafter, it is drawn up from in the solution, and the vibrating electrode is covered with the water-repelling silicone oil. A resonance frequency of said vibrating electrode is stable even after it has been left in a high temperature and a high humidity, and it is possible to prevent deterioration of a characteristic under the environmental condition in the course of use, storage and transport.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to an electrostatic electroacoustic transducer, and particularly to an improvement in a vibrating electrode used in an electret electrostatic electroacoustic transducer.

[Prior art and its problems]

An electrostatic electroacoustic transducer consists of a vibrating electrode that vibrates when acoustic energy or electrostatic energy is applied from the outside, a fixed electrode that does not vibrate even when it receives external acoustic energy or electrostatic energy, and a vibrating electrode. The main component is a spacer to maintain a constant fixed electrode spacing.

The resonant frequency of the vibrating electrode used not only in electrostatic electroacoustic transducers but also in electrical-mechanical transducers directly affects the frequency characteristics of the electrical-mechanical transducer. Of course, it is desired that the resonant frequency does not change over time, and it is also desired that the resonant frequency be kept constant even if changes in humidity or temperature occur.

However, it is possible to use an ordinary electret electrostatic electroacoustic transducer by converting P2SNAX film, which has an electrically conductive layer on one side, into an electret and using it as a vibrating electrode, or by using an electret-formed plastic film on the fixed electrode side. In the electrostatic electroacoustic transducer of the so-called pack electret type, which uses a plastic film with an electrically conductive layer on one side as the vibrating electrode material, the plastic film constituting the vibrating electrode. However, due to moisture absorption, the electrodes loosened, and the resonant frequency of the vibrating electrodes decreased significantly, causing deterioration of the characteristics of the electroacoustic transducer.

As a technique for solving the above-mentioned problems, Japanese Patent Application Laid-Open No. 48-61128 discloses an electroacoustic transducer in which the peripheral edge of an electret moisture-absorbing and relaxing film is covered with a moisture-absorbing shrinkable film to form a vibrating electrode. An apparatus is disclosed.

As is well known, in order to maintain a constant resonance frequency of a vibrating electrode with a fixed peripheral edge of a thin film, it is necessary to maintain a constant tension on the membrane.
In order to put the technology disclosed in No. 8 into practice, it is extremely difficult to certify the combination of a moisture-absorbing, relaxing film and a moisture-absorbing, shrinkable film, and it also requires a complicated process of lining the periphery of the moisture-absorbing, relaxing film with a moisture-absorbing, shrinkable film. This method requires additional steps and also has the disadvantage of increasing the mass of the vibrating part.

Additionally, single-sided metallized polyethylene tele7 talate film, which is currently used as the vibrating electrode material for pack electret capacitor microphones, which are the most numerous pack electret electroacoustic transducers on the market, is usually When the humidity is high in the microphone operating temperature range, it shows relaxation, and when the microphone's normal operating temperature is exceeded and the relative humidity is high, for example
It shows shrinkage in an atmosphere of 95% relative humidity, making it unsuitable to use single-sided polyethylene terephthalate film as a vibrating electrode material in electrostatic electroacoustic transducers without treatment. The inventors discovered this by measuring the resonance frequency of a vibrating electrode and testing the characteristics of a microphone.

[Purpose of the invention]

The present invention provides that the characteristics of a capacitive electroacoustic transducer do not deteriorate in the normal usage environment, and further, that it does not deteriorate in harsh environments that may be encountered during storage or transportation of the capacitive electroacoustic transducer. The object of the present invention is to provide an electrostatic electroacoustic transducer whose characteristics do not deteriorate even under various conditions by improving the vibrating electrode.

[Summary of the invention]

The electrostatic electroacoustic transducer of the present invention is a transducer that uses a thin film material formed by providing a frost-conducting thin film layer on at least one side of a dielectric thin film as a vibrating electrode material. It is characterized in that both main surfaces are coated with a water-repellent material.

A single-sided metallized plastic film or double-sided metalized glasstex film, which is used as a vibrating electrode material for ordinary electrostatic electroacoustic transducers, is sandwiched between a pair of diaphragm-stretching frames and then vibrated. Place it on the membrane stand,
Vibration in the shape shown in Figure 1 is achieved using the conventional method of fixing an electrically conductive ring for fixing a vibrating electrode to the metallized surface of the film after removing wrinkles in the film plane due to the weight of the frame for stretching the vibrating membrane. One membrane pole is obtained.

Next, a water-repellent substance such as silicone oil, silicone resin, fluorine-based surfactant, solvent-soluble fluorine-based oil, and solvent-soluble fluorine-based resin is dissolved in a removable solvent. After the vibrating electrode is immersed, it is pulled out of the solution and a thin insertable/extractable thin film layer is provided on both main surfaces of the vibrating electrode material.

The vibrating electrode for an electrostatic electroacoustic transducer obtained in this manner exhibits a constant resonant frequency under the normal temperature and humidity environment in which the electrostatic electroacoustic transducer is used.
After leaving it in a constant temperature and humidity chamber adjusted to a relative humidity of 95% at 0° C. for a day and night, if it is returned to normal temperature and humidity, the four-axis frequency will return to its original value.

The vibrating electrode for an electrostatic electroacoustic transducer of the present invention, which is made water repellent by surface-treating both main surfaces of the conventional vibrating electrode described above, does not loosen due to humidity in the air, and does not loosen due to humidity in the air. However, the characteristics of the electrostatic electroacoustic transducer using the vibrating electrode according to the present invention are always kept constant in practical use because the transducer quickly returns to its original state at room temperature and humidity.

〔Effect of the invention〕

According to the present invention, an expensive metal foil such as titanium foil is not used as a vibrating electrode material, and it can be normally used without going through a complicated process such as overlapping a moisture-absorbing relaxing film and a moisture-absorbing shrinkable film. It is possible to obtain a vibrating electrode that does not relax or contract even when humidity changes by using inexpensive gold-plated plastic film as a vibrating electrode material, and it is an electrostatic type with stable characteristics. , the air-acoustic transducer can be manufactured at low cost.

In addition, the water-repellent material used in the present invention not only prevents moisture absorption in the plastics used as the vibrating electrode constituent material, but also aluminum and chromium, which are provided for the purpose of providing an electrically conductive layer on the plastic film surface. Alternatively, it also has the effect of preventing corrosion of a thin film layer such as nickel/l/.

[Embodiments of the invention]

Example-1 A polyethylene terephthalate film having a thickness of 4 μm and having a Ni-Cr alloy formed in a thin layer on one side as an electrically conductive layer using a vacuum evaporation device is stretched L, with an outer diameter of 5 mm and an inner diameter of 3.5 mm. mm genuine vibrating electrode fixing ring made of Ni-C
The r-evaporated surface and the electrically conductive adhesive were used to fix and integrate it.

The electrically conductive adhesive used was two-component epoxy adhesive K.
It was obtained by dispersing four-electrode force-Bonn fine particles and graphite fine particles, and the Ni-Cr vapor-deposited on one side of polyethylene terephthalate and the Shinre vibrating electrode fixing ring were firmly fixed.

By the above-described process, 20 vibrating electrodes with the shape shown in Fig. 1 were manufactured, and 10 of them were made of water-repellent silicone.
Oil (TSF-484 trade name, Toshiba Silicone (manufactured by Wa) was immersed in a toluene solution in which it was dissolved, then removed from the solution, and the vibrating electrode was coated with water-repellent silicone oil.The concentration of the silicone oil used was Even after citoluene was volatilized at 1.0%, no oil droplets were observed on the vibrating electrode, and the vibrating electrode was covered with a film of water-repellent silicone oil.

As described above, 10 vibrating electrodes for an electrostatic electroacoustic transducer according to the present invention whose entire surface is coated with water-repellent silicone oil, and the remaining vibrating electrodes whose surface has not been surface-treated with water-repellent silicone oil are shown. Pick up the resonance frequency of 10 electrodes 1
As a result, as shown by curve A in FIG. As shown by curve B in FIG. 2, the resonance frequency was significantly increased.

Example 2 A fluororesin water repellent FC-90'5 (
USA MINESOTA MINING AND MFG
.

1.1.1. ) After spray painting a 10% solution of lychloroethane, heat treatment was performed at 80° C. for about 3 hours.

As a result of the same test as in Example 1, the resonant frequency of the obtained vibrating electrode remained relatively unchanged even after being left in a humid atmosphere.

Example-3 A polyethylene terephthalate film (thickness: 4 μm) with aluminum vapor-deposited was used as a replacement for the polyethylene terephthalate film with Ni-Cr alloy vapor-deposited on one side used in Example-1 and Example-2. The vibrating electrode was coated with a water-repellent fluororesin in the same manner as in Example 2, except for the above. The resonant frequency of the obtained vibrating electrode did not change much even after being left in a high-temperature, high-humidity atmosphere.
Aluminum deposited even after being left in a 5% atmosphere for one week.
The thin film was not corroded.

Example 4 A polyethylene terephthalate film with a thickness of 2.5 μm and an outer diameter of 5 mm, on one side of which a thin layer of Ni-Cr alloy was provided as an electrically conductive layer using a vacuum evaporation device.
A vibrating electrode for an electrostatic electroacoustic transducer having the shape shown in FIG. 1 was obtained using a vibrating electrode fixing ring manufactured by Shinrin Co., Ltd. with an inner diameter of 3.5 m. The entire surface of the obtained vibrating electrode was coated with fluororesin water repellent FC-905 in the same manner as in Example-2.

The resonant frequency of this vibrating electrode is 5.5 KHz,
As shown by curve A in Figure 3, the resonant frequency remained constant even when the relative humidity changed, but the resonant frequency of the vibrating electrode that was not coated with a fluororesin water repellent was As shown by curve B in Figure 3, it decreased significantly as the relative humidity increased.

The implementation method and specific examples of the present invention have been described above, but the vibrating electrode for electret condenser headphones with a diameter of 60 mm obtained in the same manner as Example-4 also has the same effect as Example-4. It has been obtained.

Furthermore, although the present invention was carried out for the purpose of improving a vibrating electrode for an electrostatic electroacoustic transducer, it can also be applied to a transducer that uses a vibration-absorbing material as a vibrating part, such as an electromagnetic speaker or a carbon transducer. The present invention can also be applied to microphones and the like as a method for improving paper cones and a method for improving polyester diaphragms.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a vibrating electrode for an electrostatic electroacoustic transducer used in the present invention, FIG. 2 is a graph showing an example of the effect of implementing the present invention, and FIG. A graph showing an example of implementation effects. DESCRIPTION OF SYMBOLS 1... Polyethylene terephthalate, 3... Conductive adhesive, 2... Ni-Cr vapor deposition film, 4... Fixing ring.

Claims (3)

[Claims] (1) In an electrostatic electroacoustic transducer using a thin film material formed by providing a conductive thin film layer on at least one side of a dielectric thin film as a vibrating electrode material, both surfaces of the vibrating electrode material are coated with a water-repellent material. An electrostatic electroacoustic transducer characterized by: (2) The electrostatic charge according to claim 1, characterized in that a polyethylene terephthalate film is used as the dielectric thin film, and silicone oil or a fluorine-based surfactant is used as the water-repellent material. type electroacoustic transducer. (3) After fixing the vibrating membrane stretching frame made of a conductive material to the conductive surface of the vibrating electrode material while maintaining electrical connection, a water-repellent material layer is provided on both sides of the vibrating electrode material. A method for manufacturing an electrostatic electroacoustic transducer characterized by